Gaya APA
Pennwell, . (2003).
Oil & Gas Journal, Future Energy Supply-2, Natural Gas Potential (Week of July 21).
Houston:
Pennwell Books.
Gaya MLA
Pennwell, .
"Oil & Gas Journal, Future Energy Supply-2, Natural Gas Potential".
Week of July 21
Houston:
Pennwell Books,
2003.
Jurnal TP.